IAEA Director General Grossi, holds a meeting with South Korean Foreign Minister Park Jin in Seoul
Rafael Grossi (L), director general of the International Atomic Energy Agency (IAEA), speaks during a meeting with South Korean Foreign Minister Park Jin (not pictured) at the Foreign Ministry in Seoul, South Korea December 15, 2022. Jung Yeon-je/Pool via REUTERS. Reuters

The U.N. nuclear watchdog said on Thursday its chief Rafael Grossi will travel to Iran for "high-level meetings" as diplomats say he wants to jolt Tehran into cooperating with an investigation into uranium traces found at undeclared sites.

Iran's stonewalling of the International Atomic Energy Agency's years-long investigation into uranium traces found at three undeclared sites prompted the IAEA's 35-nation Board of Governors to pass a resolution at its last quarterly meeting in November ordering Iran to cooperate urgently with the probe.

That cooperation has not materialised and Grossi is hoping that a meeting with Raisi will help smoothe the way towards ending the deadlock, diplomats say. The board's next quarterly meeting starts on Monday.

"Director General @rafaelmgrossi will travel to Tehran for high-level meetings," the IAEA said on Twitter, confirming a visit first announced by Iran.

"The DG will hold a press conference upon his return to Vienna on Saturday, late afternoon."

Diplomats have said for weeks that Grossi wants to meet hard-line President Ebrahim Raisi on this visit. The IAEA did not spell out whom he would meet.

Since the last board meeting the IAEA has chided Iran for failing to inform it beforehand of substantial changes made to the two cascades, or clusters, of advanced centrifuges enriching uranium to up to 60% purity at its Fordow plant, which is dug into a mountain. Weapons grade is around 90%.

The IAEA is also seeking explanations from Iran on how it produced a tiny amount of uranium enriched to 83.7% from those cascades at Fordow, the second site at which Iran is enriching to up to 60%. It is possible that the "spike" was accidental, though this one was relatively large, diplomats said.